Custom OS issue with throttle cracker?...

[DSteck]

Does anybody else run into an issue with the custom OS and throttle cracker? Every car I've done with the custom OS ends up decaying out the throttle cracker as soon as the clutch is pushed in. Even if I zero out the LTIT numbers so it can't learn down, it will still default to a base running airflow that is lower than what I have in the table. For example... a current car I'm working on has 1.000 lb/min in the RAF. At hot idle, it sometimes learns down to 0.850 lb/min. When driving, if you push the clutch in, cracker disappears almost immediately and it drops straight to 0.850 lb/min RAF instead of 1.000. One car in particular doesn't even see cracker ever function at all.

This is really annoying because upon pushing the clutch in, the engine stays running, but the idle droops. If I let off the clutch and put it in neutral, cracker comes back and brings it back from sagging. Am I just completely missing something? The only cars this happens to me on are ones with the custom OS.

[printmanjackson]

that's the problem I have been fighting. I zeroed the table out and started using the adaptive idle tables.

some stuff I tried http://www.hptuners.com/forum/showthread.php?t=36653

[LSxpwrdZ]

make sure CFCO isn't activating. There was one that I did a while back for whatever reason the throttle cracker didn't work at all. I normally try to flash the latest OS to vehicles just for this reason. I'll try to dig up my file to see if it's a weird OS. It's been over a year since I worked on the particular car.

[DSteck]

What's tripping me up is this is only popping up on cars I put a custo
OS in. Stock OS cars don't seem to do this do me. It's honestly be fine if it would stop learning down even after zeroing out the LTIT stuff. I even limited the remembered STIT and it still does it. It makes no sense.

If I just had a way to get some air in while coasting with the clutch pushed in, I'd be set. I am not familiar with the rolling idle tables though.

On the car where cracker doesn't function at all... That's not entirely true. Randomly while driving, it'll quickly spike and disappear again. Lol.

[printmanjackson]

the only way I found to get air to it was disable the TC and use the proportional idle tables to add air.

you can raise the TC enable/disable but as soon as you clutch it it's gone.

[edcmat-l1]

That's typical wih C5s. The TC and TF go away completely when clutching in. It's not an OS issue, they all do that.

The only way to enable the TC is to use the rolling idle airflow tables.

Another thing I've noticed on a few of them, and not all of them, is that they'll learn the lowest TP setting in a certain cell of the base idle airflow table. This can make tuning a consistent return to idle very painful. I've only seen this on a few car though. These ones, you can't even jack up the base idle airflow to make them hang. Once they learn the lowest possible TP setting that they'll idle at, they'll return to that on clutch in. Even though the base idle air may be setup to intentionally hang the idle, they'll go right past it, and drop the throttle position all the way down. Then when you come to a stop, the STIT numbers come down.

PS, I've got hours of data logs showing both conditions. There has to be more settings/switches/tables we don't have access to.

[printmanjackson]

That's typical wih C5s. The TC and TF go away completely when clutching in. It's not an OS issue, they all do that.

The only way to enable the TC is to use the rolling idle airflow tables.

Another thing I've noticed on a few of them, and not all of them, is that they'll learn the lowest TP setting in a certain cell of the base idle airflow table. This can make tuning a consistent return to idle very painful. I've only seen this on a few car though. These ones, you can't even jack up the base idle airflow to make them hang. Once they learn the lowest possible TP setting that they'll idle at, they'll return to that on clutch in. Even though the base idle air may be setup to intentionally hang the idle, they'll go right past it, and drop the throttle position all the way down. Then when you come to a stop, the STIT numbers come down.

PS, I've got hours of data logs showing both conditions. There has to be more settings/switches/tables we don't have access to.

exactly!!!! this is what I seem to be fighting! I have yet to even be close to a hanging idle.

[DSteck]

These are F-bodies.

And what you are explaining is exactly what I'm running into. Trying to inflate the base airflow doesn't work after it drives for a while.

If I could just force 0.2 lb/min in with the clutch in, I'd be set. I've just never worked with the rolling idle tables and consequently don't know how to enable them. I'm used to Gen IV.

[edcmat-l1]

These are F-bodies.

And what you are explaining is exactly what I'm running into. Trying to inflate the base airflow doesn't work after it drives for a while.

If I could just force 0.2 lb/min in with the clutch in, I'd be set. I've just never worked with the rolling idle tables and consequently don't know how to enable them. I'm used to Gen IV.

Ah Obi Wahn, you have much to learn LOL

Yeah, that's different. A F-body should work. Those tables are IAC tables.

But if this is the case, tthat you can't make it idle hang, then using the rolling idle tables won't work 100% either. It'll make it better, until it's heat soaked, and found the base idle IAC position (or lowest TP for an ETC car). In these cases, I have a fool proof cure. Not sure I wanna post it though.

DSteck I can setup your rolling idle tables if you wanna send me the tune. [email protected] is my email.

[DSteck]

Well, I decided to not be a little bitch and actually look at rolling idle. The car is perfect now. It use to drop to 0.85 lb/min on clutch in and sag at about 650-700. I got it to sit right at 800 on clutch in just by enabling rolling idle at 2mph and putting 0.1 lb/min in the adder. The descriptions for the integral tables don't seem right though. One says it subtracts airflow if idle is LOWER than commanded. That wouldn't make sense to take out air if idle is lower.

I still don't get why F bodies are just losing the cracker completely during clutch in when they have the custom OS.

[edcmat-l1]

Well, I decided to not be a little bitch and actually look at rolling idle. The car is perfect now. It use to drop to 0.85 lb/min on clutch in and sag at about 650-700. I got it to sit right at 800 on clutch in just by enabling rolling idle at 2mph and putting 0.1 lb/min in the adder. The descriptions for the integral tables don't seem right though. One says it subtracts airflow if idle is LOWER than commanded. That wouldn't make sense to take out air if idle is lower.

That's correct, the description is incorrect.

[DSteck]

Silly Chris...

Oh well. At least this can be put to bed. I think I even prefer rolling idle over throttle cracker.

[edcmat-l1]

Silly Chris...

Oh well. At least this can be put to bed. I think I even prefer rolling idle over throttle cracker.

Technically, rolling idle is throttle cracker. It works exactly the same way. Adder table that decays with speed.

[DSteck]

I guess I mean in terms of how it functions. I like simple. Lol.

[LSxpwrdZ]

That's how I use it. Most of the automatic tranny tune files have rolling idle enabled from factory. I normally try the automatic table populations in the 6spd calibrations to start off with and tweak from there. Every car is different as you know I'm sure. Glad you got it figured out.

[printmanjackson]

you would think GM would be more consistant in writing these programs.

[Midnite Magic]

Technically, rolling idle is throttle cracker. It works exactly the same way. Adder table that decays with speed.

So they are the same thing that just acts at different times? I have a custom OS 1 bar SD on an Fbody and the Rolling idle active MPH is between 3-4, and the throttle cracker is active between 1-2 MPH

[Russ K]

Looking at the demo EFI Live 2002 ZO6, there is also a throttle cracker table in P/N that is zero. And the rolling idle table is only active if the throttle cracker table is also active.

My 2001 ZO6 with a stock or a 1 bar os, the throttle cracker table goes to 0 as soon as the clutch is in.

Already asked support about adding these tables in May and Bill said their engineer would look into it. No word yet.

Russ Kemp

[Bill@HPTuners]

Looking at the demo EFI Live 2002 ZO6, there is also a throttle cracker table in P/N that is zero. And the rolling idle table is only active if the throttle cracker table is also active.

My 2001 ZO6 with a stock or a 1 bar os, the throttle cracker table goes to 0 as soon as the clutch is in.

Already asked support about adding these tables in May and Bill said their engineer would look into it. No word yet.

Russ Kemp

The tables are in our head engineers work in queue, just alot of requests in queue prior to this one.